A former day care owner left three children alone outside for 18 minutes while she scolded another child, used the bathroom, and looked up college football schedules on her cellphone, a prosecutor told jurors Tuesday afternoon.

It was during that time that 3-year-old Max Stephens wrapped a piece of twine around his neck and hanged himself as he tried to go down the slide, according to Pete Johnson, assistant district attorney.

In his opening statement, Johnson called Janna Thompson reckless and negligent for leaving Max alone, a moment in which the toddler accidentally strangled himself. He died the next day. Thompson, 58, who owned an in-home day care in Alpharetta at which she cared for Max, has been charged with second-degree murder.

“Ladies and gentleman, 3-year-olds don’t know you can die from putting twine around your neck,” Johnson said. “But adults know you can die from putting twine around your neck.”

But Thompson’s attorneys argued that she had no idea the twine — the kind used to bind bales of pine straw — had been left in the backyard. Max’s death was the result of a freak accident, attorney Jack Garland said.

“The facts will show that though this was a terrible tragedy, she was not criminally negligent, and you can only convict her if she was,” Garland said.

Thompson, who ran Miss Janna’s Daycare from her home, had watched Max since he was an infant and also took care of his younger brother, who was 10 months old at the time, Garland said. The brothers’ mother, Heidi Stephens, had a close relationship with Thompson and chose her for childcare because of the proximity to her job. Stephens was also able to leave work and return to Thompson’s home while her sons were nursing, Garland said.

Both Max and Will Stephens were at the day care on July 8, 2014, with five other children. At 3, Max was the oldest child in Thompson’s care, and while the youngest three babies took naps, the four other children went into the backyard to play. When one girl pushed another child, Thompson took the girl inside to put her in time out, she told investigators.

“When she was inside, that didn’t mean the kids were unattended,” Garland said. “She had those windows and the door to the sun room would’ve been open.”

After being inside just a few minutes, Thompson said, she returned outside and thought Max had fallen asleep on the slide, Garland said. But then she realized Max was not breathing and she began administering CPR and called 911.

Phone records, however, showed Thompson was inside for 18 minutes, Johnson said. While inside, Thompson looked at the University of Georgia football schedule at 9:37 a.m., followed by the schedule for the University of Alabama. At 9:50, while still inside, she returned a call to her father and at 9:53, she dialed 911, Johnson said.

“She wasn’t there to take that string off of Max and say, ‘You can’t do that’ and throw the string away,” Johnson said.

According to Garland, the internet searches for football schedules lasted less than 90 seconds.

“A string is simply not something that is an obviously dangerous thing,” Garland said. “Janna was doing the best she could to care for these kids. She just didn’t know there was a string wrapped around his neck.”

The trial is expected to continue Wednesday morning in Judge Henry Newkirk’s courtroom.

Second-degree murder carries a sentence of 10 to 30 years in prison.